1. Technical Field
The present disclosure relates to a wireless signal receiver, in particular to a gain control method and module in the wireless signal receiver.
2. Description of Related Art
Currently, the communication technology develops fast, and the marketed receiver can simultaneously support different wireless communication standards, wherein the wireless communication standards are for example, wireless standards of IEEE 802.11 series, third generation mobile communication standard, and blue-tooth (BT) communication standard. The IEEE 802.11 standard based wireless local area network (WLAN) device can be the wireless fidelity (WiFi) device after being authorized. Thus, the wireless signals of the wireless wideband network may be a WiFi signal, a BT wireless signal, and/or a third generation mobile communication signal.
At least two of the above wireless signals may be simultaneously transmitted, and thus the different wireless signals may interfere with each other. When the wireless signal is to be received, the wireless signal receiver can pre-detect whether the interference signal will interfere with the wireless signal to be received. When that the interference signal will interfere with the wireless signal to be received is determined, the wireless signal receiver usually decreases the gain of the amplifier thereof, so as to avoid front end overload from causing the interference signal to damage the wireless signal to be received.
Referring to FIG. 1, FIG. 1 is a block diagram of a conventional wireless signal receiver. The conventional wireless signal receiver 1 comprises an antenna 11, a first amplifier 12, a mixer 13, a band-pass filter 14, a switch 15, a second amplifier 16, an analog-digital converter (ADC) 17 and a base band/digital signal processing (BB/DSP) circuit 18. The antenna 11 is electrically connected to the first amplifier 12, and the first amplifier 12 is electrically connected to the mixer 13. The mixer 13 is electrically connected to the band-pass filter 14 and the switch 15, and the band-pass filter 14 and the switch 15 are electrically connected to the second amplifier 16. The second amplifier 16 is electrically connected to the ADC 17, and the ADC 17 is electrically connected to the BB/DSP circuit 18, and the BB/DSP circuit 18 is electrically connected to the first amplifier 12 and the second amplifier 16.
The antenna 11 is used to receive a wireless signal and to transmit the received wireless signal to the first amplifier 12. The first amplifier 12 can be a front end amplifier, such as a low noise amplifier (LNA), and is used to amplify the received wireless signal based on a first gain (i.e. front end gain) to generate a first amplified signal to the mixer 13. The mixer 13 receives a local oscillating signal LO and the first amplified signal, and mixes the local oscillating signal LO and the first amplified signal to generate mixed signal.
When the conventional wireless signal receiver 1 pre-detects whether the interference signal will interfere with the wireless signal to be received, the switch 15 is turned on, and thus the mixed signal does not pass the band-pass filter 14. When the conventional wireless signal receiver 1 has pre-detected whether the interference signal will interfere with the wireless signal to be received, the switch 15 is turned off, and thus the mixed signal passes the band-pass filter 14. The band-pass filter 14 performs band-pass filtering on the mixed signal to generate a band-pass signal.
The second amplifier 16 can be a variable gain amplifier (VGA). According to the turned-on or turned-off state of the switch 15, the second amplifier 16 amplifies the mixed signal or band-pass signal based on the second gain to generate a second amplified signal. To put it concretely, when the switch 15 is turned on, the second amplifier 16 amplifies the mixed signal based on the second gain; when the switch 15 is turned off, the second amplifier 16 amplifies the band-pass signal based on the second gain.
The ADC 17 performs analog-digital conversion on the second amplified signal to generate a digital output signal. The BB/DSP circuit 18 receives the digital output signal, and performs digital signal processing on the digital output signal to generate a first gain control signal and a second gain control signal. The first amplifier 12 can adjust the first gain thereof according to the first gain control signal, and the second amplifier 16 can adjust the second gain thereof according to the second gain control signal.
Referring to FIG. 1 and FIG. 2, FIG. 2 is a schematic diagram showing the wireless signal received by the conventional wireless signal receiver is interfered by the interference wireless signal. In FIG. 2, the wireless signal which will be received by the conventional wireless signal receiver 1 can be the BT packet. Firstly, the conventional wireless signal receiver 1 performs synchronization lock, wherein the consuming time for synchronization lock is 65 μs.
Next, the switch 15 is turned on, and maintains for 15 μs, and the second amplifier 16 amplifies the mixed signal in the 15 μs. Meanwhile, when the WiFi interference 23 exists, the mixed signal is the result which the WiFi interference 23 and wideband received signal strength indicator (RSSI) 21 mix with the local oscillating signal LO. The BB/DSP circuit 18 can determine whether WiFi interference 23 interferes with the BT packet to be received according to the digital output signal, and outputs the first gain control signal to decrease the first gain of the first amplifier 12.
Next, when the switch 15 is turned off, the conventional wireless signal receiver 1 consumes about 50 μs or more to perform auto-gain control (AGC). After the AGC is performed, the conventional wireless signal receiver 1 is able to start to obtain the payload of the BT packet.
When obtaining the payload or performing the AGC (p.s. the second amplifier 16 now amplifies the band-pass signal), if the WiFi interference 24 exists, the mixed signal is the results which the WiFi interference 24 and the narrow band RSSI 22 mix with the local oscillating signal LO. Since the amount of the WiFi interference 24 existed in the band-pass signal is less, the BB/DSP circuit 18 cannot determine that the WiFi interference 24 interferes with the currently received BT packet according to the digital output signal, the first gain does not decrease, and it causes the front end overload (i.e. the WiFi interference 24 will damage the currently received BT packet).